Cannot access serial port

[Heather]

Hi, Im having trouble accessing my serial port since I
upgraded to XP pro. Applications give error messages such
as "Com port in use". I have no software running that I
can see that is holding the port and I have checked
startup and taskmanager processes.

The comm port is enabled in bios and shows normally in
device manager. I am having this problem with a few pcs
at the moment since our company upgraded.

I have tried writing a couple of lines in VB6 to try and
open the com port:

if mscomm1.portopen = false then
mscomm1.portopen = true
end if

When running this, I had a breakpoint on the first line,
the program would step into the second line (which
suggests the comm port is not responding as open) but on
executing the port open command would give error
message "port already open". This doesnt make sense!

Can anybody help?

 

[Thomas Lutz]

There are two possibilities that you might look into.
The first thing that you might try is deleting the COM port from the
device manager in the control panel and restarting your PC and letting
Windows reinstall the port.
The other possibility is that if you have a device connected to the
port and the device outputs data either continually or when the port
is opened, Windows may be mistaking the device for a mouse when it
starts up and installing the a mouse driver for the port.
The following article discusses this issue and how to deal with it:
http://www.taltech.com/support/troublsht/NTDetect.htm


For more serial I/O tips, tricks and utilities, visit: www.taltech.com